This invention relates to relatively insensitive explosives and more particularly to the sensitization of such explosives.
A typical insensitive explosive is provided by inorganic nitrates. One such explosive is known as ANFO, or Ammonium Nitrate Fuel Oil. ANFO formed from (94%) Ammonium Nitrate and (6%) Fuel Oil was first used on the Mesabi Range in 1955 in connection with blasting for iron ore deposites. ANFO will not react explosively by itself, but will explode when energized by a high energy booster. A typical use is to fill voids in bore holes.
Since 1955 there have been numerous modifications in ANFO seeking to facilitate the initiation of the explosive reaction without adverse consequences.
One modification of ANFO is provided by Slurried Blasting Agents or SBA's. They contain ANFO with water, a gelling agent, an emulsifier, and a sensitizer. An example is provided in U.S. Pat. No. 3,113,059 in which aluminum and/or trinitrotoluene (TNT) are the principal sensitizers, Gaur (ox gum) is a thickener, and ethylene glycol is an emulsifier. SBAs have a high packing density due to their fluidity but require a strong booster for detonation.
They are also cap-sensitive explosives based on ANFO. An example is the dry seismic explosive described in U.S. Pat. No. 4,528,049. Hexamine and its nitramine derivatives are used to sensitize the composition. Small quantities of aluminum provide an additional sensitizer.
There are ammonium nitrate-hydrocarbon blasting compositions as well. Of particular interest is U.S. Pat. No. 3,580,753 in which the main explosive sensitizer is TriMethylol Ethane TriNitrate or TMETN. TMETN is oxygen deficient and therefore acts as a reducing agent for ammonium nitrate. To assure appropriate cap sensitivity, a substantial amount of TMETN is needed, which leads to an exudate of the TMET known as sweating.
Unfortunately the addition of hydrocarbons generally tends to the reduction of sensitivity. The resultant detonation velocities are 4000 meters per second or less.
Accordingly it is an object of the invention to enhance the sensitivity of relatively insensitive high explosives such as inorganic nitrates. A related object is to do so for ammonium nitrate.
Another object of the invention to increase the detonation velocities of relatively insensitive explosives such as ammonium nitrate.
A further object of the invention is to increase the sensitivity of explosives such as ammonium nitrate without objectionable sweating. A related object is to realize explosive mixtures that do not readily cause headaches from handling.
A still further object is to realize low cost explosives with high detonation velocities and long shelf lives.
Yet another object is to realize explosive mixtures that have wide ranges of sensitivity and brisance.